2. 判断二叉树是否相等

解题思路：递归

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 * };
 */

class Solution {
public:
    /**
     * 
     * @param p TreeNode类 
     * @param q TreeNode类 
     * @return bool布尔型
     */
    bool isSameTree(TreeNode* p, TreeNode* q) {
        // write code here
        if (p == nullptr || q == nullptr)
        {
            return p == q;
        }
        if (p->val != q->val)
        {
            return false;
        }
        bool left = isSameTree(p->left, q->left);
        bool right = isSameTree(p->right, q->right);
        return left && right;
    }
};